Similar to the extensor stretch, this will loosen the muscles in your forearm and help with arm pump sufferers. However, now we will focus on the flexor muscles on the inside of your forearm. To perform this stretch, extend one arm out, forearm facing up, and with your opposite hand, place your thumb under your outstretched wrist, wrap your fingers around your palm, and pull toward your body. You can also use a wall by pushing your outstretched arm, fingers up, against a wall. You should feel this stretch across your entire inner forearm. Hold for 30 seconds per arm.